The present invention relates to a new and distinct cultivar of the ornamental flowering shrub Lagerstroemia L., commonly known as crapemyrtle, and hereafter referred to by the varietal denomination ‘Gamad III’. The new crapemyrtle originated from open-pollinated seed of ‘Gamad V’ (U.S. Plant patent application Ser. No. 11/205,282) a compact, pink flowered introduction in 2005 ‘Gamad III’ was selected as a single white-flowered seedling with colorful foliage from 125 seedlings from ‘Gamad V’ in 1999 by the inventor at Dearing, Ga.